Glass

Abstract

We have invented a glass that has excellent productivity (especially resistance to devitrification), a high specific Young's modulus, and little thermal shrinkage during the manufacturing process of p-Si TFTs. [Solution] The glass of the present invention has a glass composition containing, in mass %, 55-70% SiO2, 15-25% Al2O3, 1-5% B2O3, 0-0.5% Li2O + Na2O + K2O, 0-4% MgO, 3-11% CaO, 0-4% SrO, and 0-11% BaO, and is characterized by having a strain point higher than 715°C.

Description

[Technical field]

[0001] The present invention relates to glass, and more particularly to glass suitable for use as a substrate for an organic EL display. [Background technology]

[0002] Electronic devices such as organic electroluminescence (EL) displays are thin, have excellent video display capabilities, and consume little power, so they are used in applications such as mobile phone displays.

[0003] Glass plates are widely used as substrates for organic electroluminescence displays. Glass plates for this purpose are required to have the following characteristics: (1) The content of alkali metal oxides is low to prevent diffusion of alkali ions into the semiconductor material formed during the heat treatment process; (2) To reduce the cost of glass sheets, the glass must be highly productive, and in particular, must have excellent resistance to devitrification and melting properties. (3) A high strain point is required to reduce thermal shrinkage during the manufacturing process of p-Si TFTs. (4) The specific Young's modulus must be high in order to reduce deflection due to its own weight during the transportation process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2009-525942 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0005] To elaborate on (3) above, the manufacturing process for p-Si TFTs includes a heat treatment step at 400 to 600°C, which causes minute dimensional changes in the glass plate called thermal shrinkage. If the thermal shrinkage is large, the pixel pitch of the TFT will shift, causing display defects. In the case of organic EL displays, even dimensional shrinkage of a few ppm can cause display defects, so glass plates with low thermal shrinkage are required. The higher the heat treatment temperature to which the glass plate is subjected, the greater the thermal shrinkage.

[0006] One method for reducing the thermal shrinkage of a glass sheet is to anneal the glass sheet at approximately the annealing point after forming the glass sheet, but the annealing process takes a long time, which increases the manufacturing cost of the glass sheet.

[0007] Another method is to increase the strain point of the glass plate. The higher the strain point, the less likely thermal shrinkage occurs during the manufacturing process of p-Si TFT. For example, Patent Document 1 discloses a glass plate with a high strain point. However, a high strain point can lead to a decrease in productivity.

[0008] The present invention has been made in view of the above circumstances, and its technical objective is to invent a glass which has excellent productivity (particularly, resistance to devitrification), a high specific Young's modulus, and furthermore, small thermal shrinkage during the manufacturing process of p-Si TFTs. [Means for solving the problem]

[0009] The inventors of the present invention have found that the above technical problems can be solved by strictly controlling the glass composition and strain point of low-alkali glass or non-alkali glass through various experiments, and propose this as the present invention. That is, the glass of the present invention is characterized by having a glass composition of SiO2 55-70%, Al2O3 15-25%, B2O3 1-5%, Li2O+Na2O+K2O 0-0.5%, MgO 0-4%, CaO 3-11%, SrO 0-4%, and BaO 0-11%, and a strain point higher than 715°C. Here, "Li2O+Na2O+K2O" refers to the total amount of Li2O, Na2O, and K2O. "Strain point" refers to a value measured based on the method of ASTM C336.

[0010] Secondly, the glass of the present invention preferably contains, in mass %, 55-70% SiO2, 15-25% Al2O3, 1.5-4% B2O3, 0-less than 0.1% Li2O+Na2O+K2O, 0-3% MgO, 4-10% CaO, 1-4% SrO, and 4-11% BaO as a glass composition.

[0011] Thirdly, in the glass of the present invention, the SiO2 / Al2O3 ratio in mass percent is preferably 2.5 to 3.1.

[0012] Fourth, in the glass of the present invention, the CaO / BaO ratio in mass percent is preferably 4.0 or less.

[0013] Fifth, the glass of the present invention preferably further contains 0.001 to 1 mass % of SnO2.

[0014] Sixth, the glass of the present invention has a specific Young's modulus, i.e., Young's modulus divided by density, of 29.5 GPa / g cm -3 Larger is preferred.

[0015] Seventh, the glass of the present invention has a high-temperature viscosity of 10 2.5 It is preferable that the temperature at which the viscosity of the polymer is 10 dPa·s is 1650°C or less. 2.5 The "temperature in poise" can be measured by the platinum sphere pull method.

[0016] Eighth, the glass of the present invention preferably has a liquidus temperature lower than 1310° C. Here, the “liquidus temperature” can be calculated by placing a glass powder that has passed through a standard sieve of 30 mesh (500 μm) and remains on a 50 mesh (300 μm) sieve in a platinum boat, and then holding the boat in a temperature gradient furnace for 24 hours to measure the temperature at which crystals precipitate.

[0017] Ninth, the glass of the present invention has a viscosity of 10 at the liquidus temperature. 4.2 It is preferable that the viscosity is dPa·s or more. Here, the "viscosity at the liquidus temperature" can be measured by the platinum sphere pull-up method.

[0018] Tenth, the glass of the present invention is preferably in the form of a flat plate and has an overflow joining surface at the center in the plate thickness direction, that is, it is preferably formed by an overflow downdraw method.

[0019] Eleventh, the glass of the present invention is preferably used in an organic EL device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The glass of the present invention is characterized by containing, in mass %, SiO2 55-70%, Al2O3 15-25%, B2O3 1-5%, Li2O+Na2O+K2O 0-0.5%, MgO 0-4%, CaO 3-11%, SrO 0-4%, and BaO 0-11%. The reasons for limiting the content of each component as described above are as follows. In the explanation of the content of each component, % denotes mass % unless otherwise specified.

[0021] SiO2 is a component that forms a glass skeleton and increases the strain point. The content of SiO2 is 55 to 70%, preferably 58 to 64%, and particularly 59 to 62%. If the content of SiO2 is low, the strain point and acid resistance tend to decrease, and the density tends to increase. On the other hand, if the content of SiO2 is high, the high-temperature viscosity increases, the melting property tends to decrease, and the balance of the glass components is lost, devitrified crystals such as cristobalite are precipitated, and the liquidus temperature tends to increase. Furthermore, the etching rate by HF tends to decrease.

[0022] Al2O3 is a component that increases the strain point and the Young's modulus. The content of Al2O3 is 15 to 25%, preferably 17 to 23%, and particularly 18 to 22%. If the content of Al2O3 is low, the strain point and the specific Young's modulus tend to decrease. On the other hand, if the content of Al2O3 is high, devitrified crystals of mullite or feldspar are precipitated, and the liquidus temperature tends to increase.

[0023] The mass % ratio of SiO2 / Al2O3 is an important component ratio for achieving both a high strain point and high devitrification resistance. As mentioned above, both components have the effect of increasing the strain point, but if the amount of SiO2 is relatively high, devitrification crystals such as cristobalite are more likely to precipitate. On the other hand, if the amount of Al2O3 is relatively high, devitrification crystals of alkaline earth aluminosilicates such as mullite and anorthite are more likely to precipitate. Therefore, quality% The ratio SiO2 / Al2O3 is preferably from 2.5 to 4, from 2.6 to 3.5, from 2.7 to 3.3, in particular from 2.7 to 3.1.

[0024] B2O3 is a component that enhances meltability and devitrification resistance. The content of B2O3 is 1 to 5%, preferably 1.5 to 4%, more than 1.5 to 3%, and particularly 2 to less than 3%. If the content of B2O3 is small, the meltability is likely to decrease and the liquidus temperature is likely to increase. Furthermore, the resistance to buffered hydrofluoric acid (BHF resistance) is likely to decrease. On the other hand, if the content of B2O3 is large, the strain point, acid resistance, and specific Young's modulus are likely to decrease. In addition, moisture is likely to be mixed into the glass from the raw material for introducing B2O3, and the β-OH value is likely to increase. In addition, if it is desired to increase the strain point as much as possible, the content of B2O3 is preferably 1 to less than 3%, and if it is desired to increase the meltability as much as possible, the content of B2O3 is preferably more than 3 to 5%.

[0025] Li2O, Na2O and K2O are components that increase the melting property and reduce the electrical resistivity of the molten glass, but if Li2O, Na2O and K2O are contained in large amounts, there is a risk of contamination of the semiconductor material due to the diffusion of alkali ions. Therefore, the content of Li2O + Na2O + K2O is 0 to 0.5%, preferably 0.01 to 0.3%, 0.02 to 0.2%, and particularly less than 0.03 to 0.1%. The content of Na2O is preferably 0 to 0.3%, 0.01 to 0.3%, 0.02 to 0.2%, and particularly less than 0.03 to 0.1%.

[0026] MgO is a component that enhances meltability and Young's modulus. The content of MgO is 0 to 4%, preferably 0 to 3%, 1 to 3%, and particularly 2 to 3%. If the content of MgO is low, it becomes difficult to ensure rigidity and meltability is likely to decrease. On the other hand, if the content of MgO is high, devitrified crystals of mullite and cristobalite are likely to precipitate and the strain point may be significantly decreased.

[0027] CaO is a component that reduces high-temperature viscosity and significantly improves melting property without lowering the strain point. CaO is also a component that reduces raw material costs because the raw materials used are relatively inexpensive among alkaline earth metal oxides. It is also a component that increases Young's modulus. The CaO content is 3 to 11%, preferably 4 to 10%, 5 to 10%, and particularly 5 to 9%. If the CaO content is low, it is difficult to obtain the above effects. On the other hand, if the CaO content is high, the glass becomes more likely to devitrify and the density is more likely to increase.

[0028] SrO is a component that suppresses phase separation and enhances devitrification resistance. Furthermore, it is a component that lowers high-temperature viscosity and enhances melting property without lowering the strain point. On the other hand, if the SrO content is high, the balance of glass components is lost, and feldspar-based devitrification crystals are likely to precipitate, which in turn tends to reduce devitrification resistance. Therefore, the SrO content is 0 to 4%, preferably 0 to 3%, 0 to 2.5%, and particularly 0.5 to 2.5%.

[0029] Among alkaline earth metal oxides, BaO is a component that is highly effective in suppressing the precipitation of mullite-based and anorthite-based devitrified crystals. The content of BaO is preferably 0 to 11%, 2 to 11%, 3 to 11%, 4 to 9%, and particularly 5 to 8%. If the BaO content is low, mullite-based and anorthite-based devitrified crystals are likely to precipitate. On the other hand, if the BaO content is high, Ba-containing devitrified crystals are likely to precipitate, and the high-temperature viscosity becomes too high, which tends to reduce the melting property.

[0030] The CaO / BaO mass% ratio is an important component ratio for suppressing the precipitation temperature of anorthite crystals. The CaO / BaO mass% ratio is preferably 4.0 or less, 3.5 or less, 3.0 or less, or 2.5 or less, particularly preferably 0.1 to 2.0.

[0031] In addition to the above components, the following components may be added:

[0032] ZnO is a component that enhances meltability, but if a large amount of ZnO is contained, the glass becomes more susceptible to devitrification and the strain point is more likely to decrease. Therefore, the ZnO content is preferably 0 to 5%, 0 to 3%, 0 to 0.5%, particularly preferably 0 to 0.2%.

[0033] P2O5 is a component that increases the strain point, but if a large amount of P2O5 is contained, the glass becomes more susceptible to phase separation. Therefore, the content of P2O5 is preferably 0 to 1.5%, 0 to 1.2%, and particularly preferably 0 to less than 0.1%.

[0034] TiO2 is a component that lowers high-temperature viscosity and enhances melting property, and also suppresses solarization resistance, but if TiO2 is contained in a large amount, the glass becomes colored and the transmittance is likely to decrease. Therefore, the content of TiO2 is preferably 0 to 5%, 0 to 3%, 0 to 1%, and particularly preferably 0 to 0.02%.

[0035] ZrO2, Y2O3, Nb2O5, and La2O3 have the effect of increasing the strain point and Young's modulus. However, if the content of these components is high, the density tends to increase. Therefore, the contents of ZrO2, Y2O3, Nb2O5, and La2O3 are preferably 0 to 5%, 0 to 3%, 0 to 1%, and 0 to less than 0.1%, and particularly preferably 0 to less than 0.05%. Furthermore, the total content of Y2O3 and La2O3 is preferably less than 0.1%.

[0036] Fe2O3 is a component that reduces the electrical resistivity of molten glass. The content of Fe2O3 is preferably 0.001 to 0.1%, 0.005 to 0.05%, and particularly 0.008 to 0.015%. If the content of Fe2O3 is low, it is difficult to enjoy the above effects. On the other hand, if the content of Fe2O3 is high, the transmittance of the glass sheet is likely to decrease. When electric melting is performed, it is preferable to actively introduce Fe2O3, and in this case, the content of Fe2O3 is preferably 0.005 to 0.03%, 0.008 to 0.025%, and particularly 0.01 to 0.02%.

[0037] SnO2 is a component that has a good clarifying effect in the high temperature range, and also increases the strain point and reduces the high temperature viscosity. The content of SnO2 is preferably 0 to 1%, 0.001 to 1%, 0.01 to 0.5%, and particularly 0.05 to 0.3%. If the content of SnO2 is high, devitrified crystals of SnO2 tend to precipitate. If the content of SnO2 is low, it becomes difficult to enjoy the above effects.

[0038] As long as the glass properties are not impaired, F2, Cl2, SO3, C, or metal powders such as Al and Si can be added as fining agents up to 5%. CeO2, etc. can also be added as fining agents up to 1%.

[0039] As2O3 and Sb2O3 are effective as clarifiers, and although the glass of the present invention does not completely exclude the introduction of these components, it is preferable to avoid using these components as much as possible from an environmental viewpoint. Furthermore, since the inclusion of a large amount of As2O3 in the glass tends to reduce the solarization resistance, the content is preferably 0.1% or less, and it is desirable to not include it substantially. Here, "substantially not including As2O3" refers to the case where the content of As2O3 in the glass composition is less than 0.05%. Moreover, the content of Sb2O3 is preferably 0.2% or less, particularly 0.1% or less, and it is desirable to not include it substantially. Here, "substantially not including Sb2O3" refers to the case where the content of Sb ... This refers to cases where the content is less than 0.05%.

[0040] Cl has the effect of promoting the melting of low-alkali glass, and the addition of Cl can lower the melting temperature and promote the action of the fining agent. It also has the effect of lowering the β-OH value of the molten glass. However, if the Cl content is too high, the strain point is likely to decrease. Therefore, the Cl content is preferably 0.5% or less, particularly 0.001 to 0.2%. In addition, as a raw material for introducing Cl, a chloride of an alkaline earth metal oxide such as strontium chloride, or a raw material such as aluminum chloride can be used.

[0041] The glass of the present invention preferably has the following glass properties:

[0042] The glass of the present invention has a strain point of more than 715° C., preferably 720° C. or higher, 730° C. or higher, and particularly 740 to 850° C. If the strain point is low, the glass plate is prone to thermal shrinkage in the manufacturing process of p-Si·TFT.

[0043] The density is preferably 2.65 g / cm 3 Below, 2.60g / cm 3 The following, especially 2.57 g / cm 3 When the density is high, the specific Young's modulus is high, and the glass becomes more likely to bend under its own weight.

[0044] The average thermal expansion coefficient in the temperature range of 30 to 380°C is preferably 33×10 -7 ~43×10 -7 / ℃, especially 35×10 -7 ~39×10 -7 / °C. If the average thermal expansion coefficient in the temperature range of 30 to 380°C is outside the above range, it will not match the thermal expansion coefficient of the surrounding members, and peeling of the surrounding members or warping of the glass plate will easily occur. Here, the "average thermal expansion coefficient in the temperature range of 30 to 380°C" refers to a value measured with a dilatometer.

[0045] The etching rate by HF is preferably 0.8 μm / min or more, 0.9 μm / min or more, particularly 1 μm / min or more. If the etching rate by HF is low, it becomes difficult to thin the glass sheet in the slimming process. Here, the "etching rate by HF" refers to a value calculated from the etching depth when a part of the mirror-polished glass surface is masked with polyimide tape and then etched with a 5 mass % HF aqueous solution at 20°C for 30 minutes.

[0046] The liquidus temperature is preferably less than 1310° C., 1280° C. or less, particularly 1260° C. or less. If the liquidus temperature is high, devitrification crystals are generated during forming by the overflow downdraw method or the like, and the productivity of the glass sheet is likely to decrease.

[0047] The viscosity at the liquidus temperature is preferably 10 4.2 dPa s or more, 10 4.4 dPa s or more, 10 4.6 dPa s or more, 10 4.8 dPa s or more, especially 10 4.5 If the viscosity at the liquidus temperature is low, devitrification crystals will occur during forming using the overflow downdraw method, etc., and the productivity of glass sheets will tend to decrease.

[0048] High temperature viscosity 10 2.5 The temperature in dPa·s is preferably 1650° C. or less, 1620° C. or less, 1610° C. or less, in particular 1600° C. or less. 2.5 When the temperature in dPa·s becomes high, it becomes difficult to melt the glass, and the manufacturing cost of the glass plate rises.

[0049] The specific Young's modulus is preferably greater than 29.5 GPa / g cm-3 and less than 30 GPa / g cm- 3 or more, 30.5 GPa / g cm -3 Above 31 GPa / g cm -3 If the specific Young's modulus is high, the glass plate is likely to bend under its own weight.

[0050] In the glass of the present invention, the strain point can be increased by decreasing the β-OH value. The β-OH value is preferably 0.30 / mm or less, 0.25 / mm or less, 0.20 / mm or less, and particularly 0.15 / mm or less. If the β-OH value is too large, the strain point is likely to decrease. If the β-OH value is too small, the melting property is likely to decrease. Therefore, the β-OH value is preferably 0.01 / mm or more, and particularly 0.05 / mm or more.

[0051] The following methods can be used to reduce the β-OH value: (1) Select raw materials with low water content. (2) Add components that reduce the water content in the glass (Cl, SO3, etc.). (3) Reduce the water content in the furnace atmosphere. (4) Bubble N2 in the molten glass. (5) Use a small melting furnace. (6) Increase the flow rate of the molten glass. (7) Use an electric melting method.

[0052] Here, the "β-OH value" refers to a value obtained by measuring the transmittance of glass using FT-IR and using the following formula: β-OH value = (1 / X)log(T1 / T2) X: Glass thickness (mm) T1: Reference wavelength 3846cm -1 Transmittance (%) T2: Hydroxyl group absorption wavelength 3600cm -1 Minimum transmittance (%) near

[0053] The glass of the present invention is preferably flat and has an overflow joining surface at the center in the thickness direction. In other words, it is preferably formed by the overflow down-draw method. The overflow down-draw method is a method in which molten glass is made to overflow from both sides of a wedge-shaped refractory, and the overflowed molten glass is drawn downward while joining at the lower end of the wedge to form a flat plate. In the overflow down-draw method, the surface that is to become the surface of the glass plate does not contact the refractory and is formed in a free surface state. For this reason, an unpolished glass plate with good surface quality can be produced at low cost, and it is easy to make the glass plate large in area and thin.

[0054] In addition to the overflow downdraw method, it is also possible to form a glass sheet by, for example, a slot downdraw method, a redraw method, a float method, or a roll-out method.

[0055] In the glass of the present invention, the thickness (plate thickness in the case of a flat plate shape) is not particularly limited, but is preferably 1.0 mm or less, 0.7 mm or less, 0.5 mm or less, and particularly 0.4 mm or less. The smaller the plate thickness, the easier it is to reduce the weight of the organic EL device. The thickness can be adjusted by the flow rate and plate drawing speed during glass production.

[0056] A method for industrially producing the glass of the present invention is a method for producing a glass sheet having a glass composition containing, in mass %, 55-70% SiO2, 15-25% Al2O3, 1-5% B2O3, 0-0.5% Li2O+Na2O+K2O, 0-4% MgO, 3-11% CaO, 0-4% SrO, and 0-11% BaO and having a strain point of 715°C or higher, which preferably comprises a melting step of feeding a prepared glass batch into a melting furnace and heating it electrically with heating electrodes to obtain molten glass, and a forming step of forming the obtained molten glass into a flat glass sheet having a thickness of 0.1-0.7 mm by an overflow downdraw method.

[0057] The manufacturing process of a glass plate generally includes a melting process, a fining process, a supplying process, a stirring process, and a forming process. The melting process is a process of melting a glass batch prepared by mixing glass raw materials to obtain molten glass. The fining process is a process of fining the molten glass obtained in the melting process by the action of a fining agent or the like. The supplying process is a process of transferring the molten glass between each process. The stirring process is a process of stirring and homogenizing the molten glass. The forming process is a process of forming the molten glass into a flat glass plate. If necessary, a process other than the above, for example, a condition adjusting process of adjusting the molten glass to a state suitable for forming, may be incorporated after the stirring process.

[0058] Conventionally, low-alkali glass has generally been melted by heating with a combustion flame of a burner when it is produced industrially. The burner is usually disposed above the melting furnace, and a fossil fuel, specifically a liquid fuel such as heavy oil or a gaseous fuel such as LPG, is used as the fuel. The combustion flame can be obtained by mixing a fossil fuel with oxygen gas. However, in this method, a large amount of moisture is mixed into the molten glass during melting, so that the β-OH value is likely to increase. Therefore, in producing the glass of the present invention, it is preferable to perform electrical heating with a heating electrode, and it is more preferable to melt the glass only by electrical heating with a heating electrode without heating with a combustion flame of a burner. This makes it difficult for moisture to be mixed into the molten glass during melting, so that it is easy to regulate the β-OH value to 0.40 / mm or less, 0.30 / mm or less, 0.20 / mm or less, and particularly 0.15 / mm or less. Furthermore, when electrical heating with a heating electrode is performed, the amount of energy per mass required to obtain molten glass is reduced, and the amount of melted volatile matter is reduced, so that the environmental load can be reduced.

[0059] The electrical heating by the heating electrode is preferably carried out by applying an AC voltage to the heating electrode provided at the bottom or side of the melting furnace so as to be in contact with the molten glass in the melting furnace. The material used for the heating electrode is preferably one that has heat resistance and corrosion resistance against the molten glass, and for example, tin oxide, molybdenum, platinum, rhodium, etc. can be used, and molybdenum is particularly preferable.

[0060] The glass of the present invention has a high electrical resistivity compared to high-alkali-containing glasses because of its small content of alkali metal oxides. Therefore, when applying electrical heating by heating electrodes to low-alkali glass, current flows not only in the molten glass but also in the refractories constituting the melting furnace, and there is a risk that the refractories constituting the melting furnace will be damaged early. In order to prevent this, it is preferable to use a zirconia-based refractory having a high electrical resistivity, particularly an electroformed zirconia brick, as the refractory in the furnace, and it is also preferable to introduce a small amount of a component (Li2O, Na2O, K2O, Fe2O3, etc.) that reduces the electrical resistivity into the molten glass (glass composition), and it is particularly preferable to introduce a small amount of Li2O, Na2O, K2O, etc. The content of Fe2O3 is preferably 0.005 to 0.03 mass%, 0.008 to 0.025 mass%, and particularly preferably 0.01 to 0.02 mass%. Furthermore, the content of ZrO2 in the zirconia-based refractory is preferably 85 mass% or more, particularly 90 mass% or more. EXAMPLES

[0061] The present invention will now be described with reference to examples.

[0062] Tables 1 and 2 show examples (samples No. 1 to 32) of the present invention. In the tables, "NA" means not measured. In the tables, the Fe2O3 content of each sample is not specified, but each sample contains 0.001 to 0.008 mass% of Fe2O3 as a trace component in the glass composition. In the tables, the β-OH value of each sample is not specified, but the β-OH value of each sample was 0.05 to 0.15 / mm.

[0063] [Table 1]

[0064] [Table 2]

[0065] First, a glass batch prepared by mixing glass raw materials to obtain the glass composition shown in the table was placed in a platinum crucible and melted at 1600-1650°C for 24 hours. When melting the glass batch, a platinum stirrer was used to stir and homogenize it. Next, the molten glass was poured onto a carbon plate and formed into a plate, after which it was slowly cooled for 30 minutes at a temperature near the annealing point. For each of the obtained samples, the average thermal expansion coefficient α in the temperature range of 30-380°C, density, β-OH value, HF etching rate, strain point Ps, annealing point Ta, softening point Ts, high temperature viscosity 10 4.5 Temperature in dPa·s, high temperature viscosity 10 4.0 Temperature in dPa·s, high temperature viscosity 10 3.0 Temperature in dPa·s, high temperature viscosity 10 2.5 The temperature in dPa·s, the liquidus temperature TL, and the liquidus viscosity logη at TL, Young's modulus, and specific modulus were evaluated.

[0066] The average thermal expansion coefficient α in the temperature range of 30 to 380° C. is a value measured with a dilatometer.

[0067] The density is a value measured by the well-known Archimedes method.

[0068] The β-OH value is a value measured by the above method.

[0069] The HF etching rate was calculated from the etching depth when a portion of a mirror-polished glass surface was masked with polyimide tape and then etched for 30 minutes in a 5 mass % HF aqueous solution at 20°C.

[0070] The strain point Ps, annealing point Ta, and softening point Ts are values ​​measured based on the methods of ASTM C336 and C338.

[0071] High temperature viscosity 10 4.5 dPa·s, 10 4.0 dPa·s, 10 3.0 dPa s and 102.5 The temperature in dPa·s was measured by the platinum sphere pulling method.

[0072] The liquidus temperature TL is the temperature at which crystals (primary phase) precipitate when a glass powder that passes through a standard 30 mesh sieve (sieve opening 500 μm) and remains on a 50 mesh sieve (sieve opening 300 μm) is placed in a platinum boat and held in a temperature gradient furnace for 24 hours.

[0073] liquidus viscosity log 10 ηTL is the viscosity of the glass at the liquidus temperature TL measured by the platinum ball pull-up method.

[0074] The Young's modulus is a value measured using a well-known resonance method. The specific Young's modulus is the value obtained by dividing the Young's modulus by the density.

[0075] As is clear from Tables 1 and 2, Samples No. 1 to 32 have a low content of alkali metal oxides, a strain point of 725°C or higher, and a high-temperature viscosity of 10 2.5 Temperature at dPa·s is 1640°C or less, liquidus temperature is 1302°C or less, and viscosity at liquidus temperature is 10 4.32 dPa s or more, specific Young's modulus 30.4 GPa / g cm ‐3 As a result, it is believed that Samples Nos. 1 to 32 can be suitably used as substrates for organic EL displays.

Claims

1. The glass composition is, in mass%, SiO ２ 55-70%, Al ２ O ３ 15-25%, B ２ O ３ 2.6-5%, Li ２ O+Na ２ O+K ２ The composition contains 0 to 0.5% O, 0 to 4% MgO, 3 to 11% CaO, 0 to 4% SrO, and 0 to 11% BaO, and is represented by the mass percentage ratio of SiO ２ / Al ２ O ３ The glass has a specific Young's modulus of 2.88 to 3.07, a liquidus temperature of less than 1310°C, and a strain point of more than 715°C.

2. The glass composition is, in mass%, SiO ２ 55-70%, Al ２ O ３ 15-25%, B ２ O ３ 2.6-4%, Li ２ O+Na ２ O+K ２ 2. The glass according to claim 1, containing 0 to less than 0.1% O, 0 to 3% MgO, 4 to 10% CaO, 1 to 4% SrO, and 4 to 11% BaO.

3. SiO in mass% ２ / Al ２ O ３ 3. The glass according to claim 1, wherein the refractive index is 2.90 to 3.

07.

4. 4. The glass according to claim 1, wherein the CaO / BaO ratio by mass % is 4.0 or less.

5. Further, SnO ２ The glass according to any one of claims 1 to 4, characterized in that it contains 0.001 to 1 mass % of

6. 6. The glass according to claim 1, wherein the specific Young's modulus is at least 30 GPa / g·cm −3 .

7. High temperature viscosity 10 ２．５ 7. The glass according to claim 1, wherein the temperature at dPa·s is 1650° C. or lower.

8. 8. The glass according to claim 1, having a liquidus temperature of 1280° C. or lower.

9. Viscosity at liquidus temperature is 10 ４．２ 9. The glass according to claim 1, having a viscosity of at least dPa·s.

10. 10. The glass according to claim 1, which has a flat plate shape and has an overflow joining surface at the center in the plate thickness direction.

11. The glass according to any one of claims 1 to 10, which is used for an organic EL device.

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